This invention relates to the control of condensation on the surface of a tank that is periodically supplied with liquid having a temperature lower by a certain amount than the temperature of the environment in which the tank is located. In particular, the invention relates to the control of condensation on a toilet tank.
The condensation of water on the outer surface of a toilet tank is well known as the source of many problems. The moist surface is conducive to the growth of fungi, and if the condensation is severe, the accumulated water may drip off, forming puddles on the floor and possibly loosening floor-covering material thereon. The water may even work down into the sub-flooring where it may eventually rot the wood. The problem is particularly acute in homes that are supplied with water that is especially cold, such as water directly from a well, which may have a temperature of about 51.degree. to 56.degree. F. Moreover, in normal operation of a toilet tank, all of the water in it is emptied out each time the toilet is flushed, and a whole new tankful is drawn in quickly.
The problem of condensation on a toilet tank has been attacked by Jones in U.S. Pat. No. 3,023,423 by providing a holding tank that receives the incoming water from the water main and holds it to allow it to warm up before it is transferred to the toilet tank. By the time the water reaches the toilet tank, it is supposed to be close enough to room temperature so that it will not cause condensation on the tank. However, the length of time the water is retained in the holding tank depends on the size of that tank and the rate at which water is drawn out of it. If the toilet is flushed several times in relatively rapid succession, as sometimes happens, the water may not stay in the holding tank long enough to heat up sufficiently. In any case, room must be provided for the holding tank, and extra plumbing must be used, which makes such a solution to the condensation problem particularly unsuitable for adding onto an existing system.
Toye (U.S. Pat. No. 2,659,898), Starr (U.S. Pat. No. 2,895,140), and Rom (U.S. Pat. No. 2,900,645) mix hot water with the cold water to avoid condensation. Their systems also require extra plumbing not normally connected to a toilet.
Bosworth (U.S. Pat. No. 2,527,115) electrically heats the water in the tank. The electrical current is passed through a thermostatically controlled switch that mechanically coacts with a float on a pivotally mounted arm. The heater is actuated before the tank fills up, and it could burn out if the flush valve stuck in the open position, as happens from time to time.